Horton

Re: remaining sql/json patches

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: Amit Langote <amitlangote09@gmail.com>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Andres Freund <andres@anarazel.de>, Erik Rijkers <er@xs4all.nl>, Andrew Dunstan <andrew@dunslane.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2024-01-22T06:14:07Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. SQL/JSON: Various improvements to SQL/JSON query function docs

  2. SQL/JSON: Fix some obsolete comments.

  3. SQL/JSON: Fix issues with DEFAULT .. ON ERROR / EMPTY

  4. JSON_TABLE: Add support for NESTED paths and columns

  5. Fix JsonExpr deparsing to emit QUOTES and WRAPPER correctly

  6. Fix typo introduced in 6185c9737

  7. Add basic JSON_TABLE() functionality

  8. Avoid splitting errmsg string to span multiple lines

  9. Add SQL/JSON query functions

  10. Implement various jsonpath methods

  11. Add soft error handling to some expression nodes

  12. Adjust populate_record_field() to handle errors softly

  13. Refactor code used by jsonpath executor to fetch variables

  14. Test EXPLAIN (FORMAT JSON) ... XMLTABLE

  15. Simplify productions for FORMAT JSON [ ENCODING name ]

  16. Add trailing commas to enum definitions

  17. doc: add missing <returnvalue> and whitespace

  18. Add more SQL/JSON constructor functions

  19. Rename a nonterminal used in SQL/JSON grammar

  20. Some refactoring to export json(b) conversion functions

  21. Don't include CaseTestExpr in JsonValueExpr.formatted_expr

  22. Code review for commit b6e1157e7d

  23. Pass constructName to transformJsonValueExpr()

  24. Unify JSON categorize type API and export for external use

  25. Make some indentation in gram.y consistent

  26. Allow most keywords to be used as column labels without requiring AS.

  27. Reduce size of backend scanner's tables.

  28. Use perfect hashing, instead of binary search, for keyword lookup.

Attachments

I found two main issues regarding cocece SQL/JSON function output to
other data types.
* returning typmod influence the returning result of JSON_VALUE | JSON_QUERY.
* JSON_VALUE | JSON_QUERY handles returning type domains allowing null
and not allowing null inconsistencies.

in ExecInitJsonExprCoercion, there is IsA(coercion,JsonCoercion) or
not difference.
for the returning of (JSON_VALUE | JSON_QUERY),
"coercion" is a JsonCoercion or not is set in coerceJsonFuncExprOutput.

this influence returning type with typmod is not -1.
if set "coercion" as JsonCoercion Node then it may call the
InputFunctionCallSafe to do the coercion.
If not, it may call ExecInitFunc related code which is wrapped in
ExecEvalCoerceViaIOSafe.

for example:
SELECT JSON_QUERY(jsonb '[1,2]', '$' RETURNING char(3));
will ExecInitFunc, will init function bpchar(character, integer,
boolean). it will set the third argument to true.
so it will initiate related instructions like: `select
bpchar('[,2]',7,true); ` which in the end will make the result be
`[,2`
However, InputFunctionCallSafe cannot handle that.
simple demo:
create table t(a char(3));
--fail.
INSERT INTO t values ('test');
--ok
select 'test'::char(3);

however current ExecEvalCoerceViaIOSafe cannot handle omit quotes.

even if I made the changes, still not bullet-proof.
for example:
create domain char3_domain_not_null as char(3) NOT NULL;
create domain hello as text NOT NULL check (value = 'hello');
create domain int42 as int check (value = 42);
CREATE TYPE comp_domain_with_typmod AS (a char3_domain_not_null, b int42);

SELECT JSON_VALUE(jsonb'{"rec": "(abcd,42)"}', '$.rec' returning
comp_domain_with_typmod);
will return NULL

however
SELECT JSON_VALUE(jsonb'{"rec": "abcd"}', '$.rec' returning
char3_domain_not_null);
will return `abc`.

I made the modification, you can see the difference.
attached is test_coerce.sql is the test file.
test_coerce_only_v35.out  is the test output of only applying v35 0001
to 0007 plus my previous changes[0].
test_coerce_v35_plus_change.out is  the test output of applying to v35
0001 to 0007 plus changes (attachment) and previous changes[0].

[0] https://www.postgresql.org/message-id/CACJufxHo1VVk_0th3AsFxqdMgjaUDz6s0F7%2Bj9rYA3d%3DURw97A%40mail.gmail.com